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Blue Ringed Octopus


One of the highlights of the holiday season, here in Australia, is being able to go to the beach (please don’t try this in the north). Victoria is one of the safer states when it comes to dangerous critters but the local news has reported sightings of another of the ‘world’s deadliest creatures’ at my local beach. I thought it about time to revise the dangers of the Blue Ringed Octopus.

This cute-appearing creature weighs in at just a few hundred grams but is listed in the top ten of the world’s most deadly creatures. The Blue Ringed Octopus (Hapalochlaena sp.) actually not just a single species but three or four that live in tide pools and coral reefs. They normally go about their day-to-day business, feeding on small crab or shrimp until disturbed by some hapless rock pool exploring child.

Blue-ringed octopus distribution – from

The bite is usually innocuous, barely noticed by the victim as the small beak penetrates the skin. Within five to 10 minutes, the toxin-containing saliva has made it into the bloodstream. The victim may be rendered mute as the toxin affects the muscles of the tongue, followed by progressive flaccid paralysis. As the respiratory muscles are affected, they may collapse, unable to catch their breath. As cardiac muscle is unaffected, the victim suffers, often in silence, until cerebral hypoxia and death ensue.

The saliva contains maculotoxin, a toxin that is identical to tetrodotoxin. They don’t actually produce the toxin themselves but accumulate it from the environment, probably from a Vibrio strain of bacteria. It works by blocking sodium channels in neurons and skeletal muscles leading to numbness and paralysis. Fortunately, the tentacles are toxin free so you can pick them up – very carefully.

How should you treat the victim?

Like a lot of toxicology and toxinology, this is an evidence-free area. Pressure-immobilisation bandaging in the immediate pre-hospital phase may lessen the spread of the toxin until emergency transportation arrives.

Given that death is caused by respiratory embarrassment, rapid sequence intubation and ventilation coupled with excellent ICU supportive management is the mainstay of treatment.

There is no antidote to the toxin.

Just how deadly is it?

There have only been two reported fatalities in Australia. The first, in 1954, was a 21 year old sailor, Kirk Dyson-Holland, that died within two hours of being bitten. Others have been more lucky and have survived through judicious use of artificial ventilation.

“The patient held it on the back of the hand for a minute of two, and after putting it down noticed a speck of blood on his hand, there had been no sensation of sting or bite. A few minutes later he felt a prickling sensation around his mouth which rapidly became generalized and within fifteen minutes was almost completely paralysed…..Just after admission spontaneous respiration ceased and he was respired for about an hour. Thereafter he made a steady and uneventful recovery of his muscle power. He was well the next day, chest X-ray was clear and he was discharged.”

regarding Arthur Ricketts, bitten on Christmas Day 1962

So, with just a couple of deaths ever reported in Australia can it really be that dangerous? The maculotoxin rates as 1400 mouse units per gram*.

The bottom line

If someone collapses on or near the beach, paralysed after a seemingly minor bite, then consider the Blue Ringed Octopus.

* What is a mouse unit? It’s a biological measure of toxicity.


Murray L, Daly FFS, Little M, and Cadogan M. Chapter 5.12 Blue-Ringed Octopus; in Toxicology Handbook, Elsevier Australia, 2007

Report of the first fatality in Australia: Flecker H, Cotton BC (1955). Fatal bite from an octopus. Med J Aust 2:329-331

Injuries to man from marine invertebrates in the Australian Region. Cleland, J. B. and Southcott, R. V. 1965. National Health and Medical Research Council, Canberra, pp282

Miyazawa K, Noguchi T. Distribution and origin of tetrodotoxin. Journal of Toxicology: Toxin Reviews. 2001 Jan 1;20(1):11-33.
Hwang DF, Arakawa O, Saito T, Noguchi T, Simidu U, Tsukamoto K, Shida Y, Hashimoto K. Tetrodotoxin-producing bacteria from the blue-ringed octopus Octopus maculosus. Marine Biology. 1989 Feb 1;100(3):327-32.
Sheumack DD, Howden ME, Spence I, Quinn RJ. Maculotoxin: a neurotoxin from the venom glands of the octopus Hapalochlaena maculosa identified as tetrodotoxin. Science. 1978 Jan 13;199(4325):188-9.
Walker DG. Survival after severe envenomation by the blue-ringed octopus (Hapalochlaena maculosa). The Medical journal of Australia. 1982 Dec;2(12):663-5.
Cavazzoni E, Lister B, Sargent P, Schibler A. Blue-ringed octopus (Hapalochlaena sp.) envenomation of a 4-year-old boy: a case report. Clinical Toxicology. 2008 Jan 1;46(8):760-1.

Many thanks to Chris Nickson and the LITFL team for a lot of the facts.



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